I’m using the cross-platform Qt C++ library to write an app for linux, OS X, and Windows. Qt source can be compiled to a wide range of systems and devices, with two obvious omissions that are not likely to be filled any time soon: iPhone and Android. I know I am going to need client code on these devices, and I know that the client code is going to be extremely similar to the Qt client code. How do you design for this?

Applying the concept of separation of concerns, you design your classes into layers. The base layer consists of high level concept classes that perform all fundamental actions using generic data types. Then, the derived layer is used to get the job done, using the most useful and powerful lower level tools at your disposal. Push everything you can into the base layer, until you hit the limit of non-portable information and data types. It’s a beautiful way to code.

To be more specific, in my case, the base class layer will be using C++, including the STL, which gives me tons of power. I will pull in boost if even more horsepower is needed. The derived class layer for the first round of clients will be Qt-powered. The Qt library has a massive amount of real-world usefulness, supporting everything from http to video playback. I have not gotten to the iPhone and Android clients yet so the whole concept may change, but here’s my current plan. The iPhone code will be Objective C with the C++ base class layer linked in. I will attempt to incorporate the C++ base class layer into the Android code using the NDK.

Here’s a quick example of the layer approach, in this case used to quickly set up profiling using Qt’s QTime class at the lower level: (continued…)

I love my asserts. I use them like crazy throughout my code and catch errors faster than you and your whole testing department. :> The computer does exactly what I ASK of it, which sometimes is not the same as what I EXPECT of it. So I wrap up my expectations with assert macros so my computer friend and I stay on the same page. Happy happy joy joy.

In Qt, we have the Q_ASSERT macro. Qt default behavior is to abort on any Q_ASSERT macro failure. This is weird to me (even if it is common). Almost universally, I want to SEE what’s going on when I hit an assert. Sometimes the assertion turns out to be wrong and may need adjusting. Even if it’s right, sometimes it’s helpful to check the effect of the failed assertion. And certainly, being able to walk back up the stack trace is critical to determine where things went wrong. I can kill the program easily if I WANT to, but I may want to continue – it should be my choice. It’s a no-brainer!

So I don’t use Q_ASSERT. Here’s my cross-platform C++ assert macro hackery. It’s not perfect but it’s getting me by so far… (continued…)

On my recent upgrade of php to 5.3, gentoo created a new slot so that people could run 5 and 5.3 in parallel. Gentoo is always giving you options (can you handle it? “ask yourself, do you feel lucky, punk?”). As usual, you must proceed with caution. And as usual, you will probably learn something along the way. This time around, the lesson is on php.ini defaults. (continued…)

I’m the last person to praise Microsoft – with the amount of money they bleed from the human race, there is no room to give them any slack. To their credit, corporations of their magnitude almost always decay into bureaucracy and inefficiency, and they could be worse. Case in point, Visual Studio. It kicks ass. Here’s a quick rundown of what it does for me when debugging my Qt app. This is in comparison to Qt Creator, which is awesomely streamlined and elegant. But when you are debugging, every bit of comfort is gold:

• if you set things up as i did, you can step right through the Qt source with no pain
• the watch window takes far fewer steps to manipulate
• the debugger can dereference pointers better
• the debugger can dereference iterators better
• code completion in the editor can also handle dereferenced iterators
• debugger can show long strings much better
• you can step over a function back up to the caller without dropping to the next line of code in the call routine (for when multiple calls take place on one line)
• debugger doesn’t head south when often browsing out of array bounds (inevitable if you are watching variables)

I’ll add to this list as seems fit. I should probably also start a list of the advantages of Qt Creator, it is really nice to work with on linux and Mac. Including Eclipse would round out the list nicely… but for now, back to teh coding. :> Check out this recent post for instructions on getting VS set up with Qt, it’s easy.

I could not live without this hack. Placing the Windows taskbar on the lefthand side, with auto-hide on, gives you more screen real estate AND more taskbar width when it pops out when needed, via Ctrl-Esc. I’ve been configuring Windows this way for decades. How can people stand that little strip at the bottom flashing at them all day? Seems like a little thing… but to me it’s huge. It actually determines who’s in charge – am I sitting at my computer to be told what I should do via little popup notifications, or am I there to get something done, checking on any notifications when I’m ready to address them? Sure, my friends can get annoyed that I take an hour to respond to an instant message, but I’m getting stuff done. Anyway, I’ve gotta keep this thing handy… (or just resist the urge to boot into Windows to play games…) :>

UPDATE: the original hack hasn’t kept pace with Explorer updates, and hasn’t been open sourced so others can do it. On page 17 of that forum post, another hack was provided that seems to be working.